How to Hire Node.js Developers: Express, NestJS and APIs

To hire a Node.js developer for backend and API work, decide first whether your service suits Express or NestJS. Then test the person on the parts that break in production: async code, the database, background jobs, authentication, security and deployment. A short design exercise and ten focused questions tell you more than any algorithm puzzle.

This guide is for CTOs and product leads adding backend capacity to a product that already has users or funding. It draws on Node.js backends Empiric Infotech built for clients in Germany and Australia. Our own terms are on the hire Node.js developers page.

The short answer

• Describe the backend first: who calls the API, what data it holds, what runs in the background and what updates live.
• Pick Express or NestJS before you interview: Express for a small service or a working Express codebase, NestJS when several developers share one backend.
• Test production skills: async code, TypeScript, data, queues, WebSockets, authentication, security and deployment.
• Run a design exercise: an order and payment webhook problem shows how the person handles failure.
• Compare the full monthly cost: employees with employer costs, agencies and a dedicated developer.
• Keep ownership from day one: the repository, cloud accounts, database and secrets stay in your company's name.

Describe the backend before you hire

Half a page about your backend tells you which skills to test:

• Who calls the API: your web app, a mobile app, partner systems or all three. A public API needs versioning, rate limits and an OpenAPI spec.
• The data: orders, invoices and permissions that need transactions point to PostgreSQL. Flexible, document-shaped records such as content or activity feeds sit well in MongoDB.
• Work outside the request: emails, reports, imports and webhook processing belong in background jobs.
• Live updates: dashboards, chat and notifications need WebSockets.
• Rules: payments, single sign-on, audit logs and GDPR requests each add work.

Then settle the team shape. One backend developer suits an API behind a frontend your team already builds. If the same person should also build the React frontend, see hire MERN stack developers. If the gap is the interface, hire for React instead.

Express or NestJS: decide this first

The two frameworks lead to different interviews.

Express is small and unopinionated. It gives you routing and a middleware chain, and leaves folder layout, validation and error handling to the team. That is quick for one or two developers. On a bigger codebase, it needs conventions someone enforces in review: thin routes, business logic in services, request validation with a library such as Zod, and errors handled in one place.

NestJS is a TypeScript framework that runs on Express by default, or on Fastify. It adds the structure Express leaves out:

• Modules that group one domain, such as billing or users, and declare what they share.
• Dependency injection, so services receive their dependencies through the constructor and tests can swap them for mocks.
• Guards, pipes and interceptors that apply authorization, validation and logging the same way on every endpoint.
• A shared layout a new developer recognises on day one.

The trade-off is more boilerplate and a learning curve around decorators, which a service with a handful of endpoints does not need.

For BPM, a German B2B procurement platform that runs IT maintenance tendering as a transparent auction, a single dedicated developer built owner, provider and admin portals on React, TypeScript, NestJS, PostgreSQL, TypeORM, Redis and Docker. Three portals sharing one auction engine is the kind of backend where NestJS modules keep each area separate. For Architecture CRM in Australia, a single dedicated developer built a CRM that brings tasks, email, calendar and contacts into one dashboard on React, Node.js, Express.js and MongoDB, shipped with Docker.

A NestJS developer is usually at home in Express, since NestJS runs on it. The reverse takes time, so for a NestJS codebase, ask for NestJS work they have shipped.

Backend skills to test for

Syntax is the easy part. Test the areas where backend mistakes reach customers:

• The event loop and async code. JavaScript runs on one thread per process, so slow synchronous code holds up every request. Look for correct promise handling, streams for large files and worker_threads or a job for CPU-heavy work.
• TypeScript. Strict mode, types shared with the frontend, and runtime validation on every input, because types disappear when the code runs.
• Data and ORMs. PostgreSQL or MongoDB through Prisma, TypeORM or Mongoose, with migrations, indexes, transactions and no N+1 queries.
• Queues. BullMQ with Redis, retries with backoff, scheduled jobs and jobs that are safe to run twice.
• WebSockets. Socket.IO or ws, authentication when the connection opens, and a Redis adapter once more than one server runs.
• Authentication. Passwords hashed with bcrypt or Argon2, httpOnly session cookies or short-lived tokens with refresh, and single sign-on through a provider such as Auth0.
• Logging and monitoring. Structured JSON logs, a request ID on every call, error tracking such as Sentry, health checks and alerts.
• Security basics. The OWASP Top 10, including broken access control, injection and security misconfiguration: parameterised queries, rate limits on login, Helmet headers, npm audit in CI and secrets outside the repository.
• Deployment. Docker, a CI pipeline such as GitHub Actions, safe migrations and graceful shutdown on SIGTERM.

Every developer Empiric Infotech introduces has already cleared technical interviews, real-world coding tests and a portfolio review, so your interview can focus on fit with your backend.

A 45-minute API design exercise

Backend work is mostly about failure, and a design exercise shows how someone handles it. Run it on a call with a shared whiteboard.

The problem: customers place orders through your API. Payment is confirmed later by a Stripe webhook. When payment succeeds, the customer gets a confirmation email and the operations dashboard updates live. Design the backend.

1. 10 minutes of questions. Good developers ask before they draw: order volume, failed payments, who watches the dashboard, which database you run.
2. 20 minutes of design. Endpoints, tables, where the webhook lands, what goes on a queue and how the dashboard gets updates.
3. 15 minutes of failure cases. Stripe sends the same webhook twice. The email provider is down for an hour. Redis restarts.

A strong answer includes:

• Signature verification on the raw webhook body, a fast 200 response and the real work handed to a queue.
• The Stripe event ID under a unique constraint, so a repeat delivery changes nothing.
• An order status, such as pending, paid or failed, updated inside a transaction.
• A BullMQ email job with retries and a sent record, so a retry never sends twice.
• A WebSocket channel scoped so each user sees only their company's orders.
• The order ID in every log line, and an alert when jobs keep failing.

Weak answers skip the questions, jump to microservices, or never ask what happens when the webhook arrives twice.

10 questions that test backend judgment

Each question comes with what a strong answer covers.

1. One request runs a two-second synchronous loop. What happens to the others? They wait, because the loop blocks the process's only JavaScript thread. Move the work to worker_threads or a job.
2. A handler makes five independent API calls. How do you write it? Promise.all to run them together, Promise.allSettled when partial results are fine, and no await inside a loop unless order matters.
3. When would you start a new service in NestJS rather than Express? Several developers or domains, or a need for one consistent structure. Good answers also name the cost: more boilerplate.
4. How does dependency injection help you test a NestJS service? Dependencies arrive through the constructor, so Test.createTestingModule can replace a provider, such as the payment client, with a mock.
5. An endpoint slowed down as the data grew. Where do you look first? ORM query logs, EXPLAIN ANALYZE in PostgreSQL, missing indexes, N+1 queries and offset pagination on large tables. Caching comes last.
6. A BullMQ invoice job ran twice after a retry. How do you stop duplicates? A deterministic job ID, a unique constraint or sent flag checked inside the job, and handlers written to be safe to run again.
7. How do you run Socket.IO on three servers? The Redis adapter so events reach every server, sticky sessions when HTTP long-polling is on, and authentication at the handshake.
8. A user changes the order ID in the URL and sees another customer's order. What went wrong? Broken access control, the first item on the OWASP Top 10. Scope every query by user or tenant, enforce it in one guard or middleware, and test with other users' IDs.
9. What must never appear in your logs? Passwords, tokens, API keys, card numbers or excess personal data. Each line should carry a request ID, route, status and duration.
10. How do you deploy without dropping requests? On SIGTERM, stop taking connections, finish requests in flight and close the database pool. Add readiness checks, rolling deploys and migrations that add columns before removing old ones.

What a Node.js developer costs per month

The hiring model changes the monthly cost far more than the framework does. The BLS publishes no separate band for Node.js, so the US figure is the median for all software developers.

• US employee: median salary $135,980 a year, or $11,332 a month (BLS, May 2025), and about $15,298 a month with employer costs.
• UK or EU employee: about EUR 7,875 a month with employer costs.
• Australian employee: about AUD $13,455 a month with employer costs.
• Agency, junior to senior, 160 hours (Accelerance 2026): $3,840 to $6,560 in Asia, $4,960 to $12,160 in Eastern Europe, $5,280 to $12,000 in Latin America.
• Empiric Infotech dedicated developer, 2026 rate: $2,000 (EUR 2,000, AUD $3,000) for 160 to 172 hours.

Employer costs come from our software development cost benchmark. An in-house hire also takes about six weeks to fill and about $5,475 per hire in the US (SHRM 2025). For each region in detail, see dedicated developer cost per month.

The Empiric Infotech rate covers a developer who works only on your product, inside your repository, standups and release process. A senior team lead reviews and tests every release, so there is no separate QA seat.

Red flags in a backend hire

• They call the event loop multi-threaded, or cannot say what blocks it.
• SQL built by joining strings, or unvalidated input reaching the database.
• any across the TypeScript code, or strict mode turned off to silence errors.
• No plan for a webhook or job that runs twice.
• Secrets in the repository, or deploys from their personal cloud account.
• Microservices proposed for one team and one database.
• No production incident they can walk you through.

Ownership and the first two weeks

Before the first commit, put the repository, cloud account, database, DNS, Stripe account and secret manager in your company's name, and sign the NDA and IP assignment. With Empiric Infotech both are signed from day 0, and you own the code, the repository and the accounts.

In the first week, give the developer a real ticket with a clear finish and judge the pull request, its tests and the questions asked. Every Empiric Infotech engagement starts with a 7-day risk-free trial, and after that, seven days' notice ends it.

Frequently asked questions

Should we hire a NestJS developer or a Node.js developer?

A Node.js developer who has shipped NestJS, if your backend runs on it. The core skills are the same, and NestJS experience means a faster start with its modules and dependency injection.

Can one Node.js developer build our whole backend?

Yes, for most products with one API, one main database and a few integrations. Add a second developer when a frontend also needs full-time work, or live features and integrations run in parallel.

How many hours does a Node.js developer in India overlap with a UK or European team?

5 to 7 hours a day, 9:00 AM to 3:00 PM in the UK and 9:00 AM to 4:00 PM in Central Europe. That covers a morning standup, live API design and debugging together.

How quickly can a Node.js developer start?

Within 48 hours of your go-ahead, with a dedicated developer from Empiric Infotech, after you have met the developer we introduce. An in-house US hire takes about six weeks to fill.

Who owns the code, the cloud accounts and the data?

You do, fully. The NDA and IP assignment apply from day 0, and the repository and cloud accounts sit in your company's name. UK and EU clients also sign a DPA with Standard Contractual Clauses.

Can a new developer take over our existing Express API?

Yes. The first week goes on running it locally, reading the routes and data model, adding tests around the riskiest endpoints and checking dependencies with npm audit. A move to NestJS can follow, module by module.

Meet a Node.js developer

With your half-page description ready, the quickest next step is a call with a developer who has built this kind of backend. Empiric Infotech was founded in 2020, and our 75+ engineers and designers have delivered 375+ projects for 200+ clients in 25+ countries. The hire Node.js developers page has our process, the trial and each region's terms. If the same person should also own the React frontend, see hire MERN stack developers.